Apparatus for protecting power



ApriLZQ, 1947.

G. A. MATTHEWS APPARATUS FOR PROTECTING'POWER LINES Original Filed May7, 1940 4 Sheets-Sheet l dw/md 5003000 maomawomamwm Ampere:

- gfl Main/ eek; #04! m? April 29, 1947. G. A. MATTHEWS R. 22,872

- APPARATUS FOR PROTECTING POWER LINE-S Original Filed May 7, 1940 4Sheets-Sheet 2 0 F g.4. l6

' n if ft :2 43 o 6/ 57/ 77km Delay 7Z5; 9 1; Man-60min:

2/ 0i/Lere/ April 29, 1947. G. A. MATTHEWS 7 I APPARATUS FORPROTECTINGPOWER LINES I 4 Sheets-Sheet 5 Original Filed May 7, 1940 M Apfil 29,1947.

G. A. WTTHEWS APPARATU? FOR PROTECTING POWER LINES 4 Sheets-Sheet 4Original Filed May 7, 1940 r &

Reissued Apr. 29, 1947 7 George A. Matthews, Detroit, Mich, assignor toThe Detroit Edison Company, Detroit, Mich, a corporation of New YorkOriginal No. 2,352,556, dated June 27, 1944, Serial 333,875, May "I,

1940. Application for reissue August 20, 1945, Serial N0. 611,617

Claims. 1

This invention relates to apparatus for protecting electrical powerlines against damage from short circuits and/or arcing faults betweenthe line conductors. The invention is not limited to but is particularlyuseful in connection with, overhead feeder circuits of the insulated conductor type. I 1

Studies of the records of interruptions to overhead circuits show thatover 85% resulted from purely transient faults due to such causes aslightning flashover, line conductors momentarily swinging together, andsmall conductors or other foreign objects falling across the wires; andonly a small percentage of circuit interruptions are due to permanentfaults. Unfortunately, how ever, the power are that starts from atransient fault under the present systems of feeder circuit protectionfrequently results in a burn off of the line conductor, or at least indamage that so weakens the conductor as to give rise to mechanicalbreakage by wind, sleet or snow loadings.

The equipment generally employed by practically all utility companiesfor the protection of feeder circuits includes time-delay overcurrentrelays for tripping the station breaker, and reclosing equipment forobtaining one or more timed reclosures up to a lockout in the case of apermanent fault. The tripping of the station circuit breaker has beenpurposely delayed to provide a, time differential between the operationof a protective device, such as the fuse at a distribution transformeror an overload breaker on a customer's premises, as it has been thegenerally accepted plan to avoid an opening of the main feeder circuitby faults which, in theory, could be removed by local protectivedevices. The operating characteristics of such equipment, in the typicalcase of a city circuit with a relay set to trip at 500 amperes, havebeen a delay of several seconds at overloads of from 500 to 750 amperes,with a progressive decrease in the tripping time to about 30 cycles, ona 60 cycles per second alternating current distribution circuit, at 2000amperes. The delay in tripping remains approximately constant at higherfault currents, and the total circuit clearingtime for fault currents of2000 amperes or over has been about 41 cycles, i. e., the relay trippingtime plus about 11 cycles for opening the breaker contacts andextinguishing the are drawn between them. The equipment on ruralcircuits has been, in general, adjusted for a longer delay than that forcity feeder circuits.

satisfactory several years ago, but the conditions ,for which it wasdesigned have altered materially as increasing loads have resulted inthe use of substation transformers of larger size and higher shortcircuit current capacity, and the bare concluctors originally installedon suburban and rural lines have been replaced by insulated orweatherproofed copperwire to meet local ordinances. An increase in theshort circuit current in a fault obviously increases the rate at whichan arcing fault damages the conductors and, for any given fault current,insulated conductors are badly burned or melted off beforethe-stationbreaker opens as the insulation holds an arcing fault at the totalclearing time from 10 cycles to 5 cycles.

the location where it was initiated. With bare wires, the arc traveledfreely along the line until it was blown out or reached insulators whereit was usually stopped. Damage to the tie wires or to the insulatorsmight then occur but, in general, there is less likelihood of damage tobare wires than to insulated wires in the case of transient faults,

Heavier short circuit currents and insulated conductors have thuscreated such conditions that even a transient fault generally results ina burn off of the conductors of the affected branch feeder circuit andfrequently results in a. loss of service on the entire. main feedercircuits. It has been proposed to set the relays for instantaneoustripping of the station breakers, and to design the breakers for morerapid operation. Faster operation is obviously essential if burn off ofthe insulated conductors is to be avoided but the switchgear nowcommercially available cannot open a faulty 60 cycles line in less thanabout 10 cycles, and the best performance claimed for any experimentalequipment has been 5 cycles between the initiation of the fault and theopening of the line.

I have made a systematic study of the burn of! characteristics of theweatherproofed copper wire now in general use, i. e., in sizes from No.6 solid up to No. 4/0 stranded, and have found that it is not possibleto effect a substantial decrease in circuit outage from transient faultsby reducing The fact is that the short circuit current flow in an arcingfault between the insulated conductors of existing overhead distributioncircuits is of such magnitude, with respect to the wire size, thatserious damage or a complete burn of! results if the arcingfaultcontinues beyond from /2 to 2 cycles on a 60 cycles line.

The design difliculties encountered in reduc- Protective equipment ofthis type wasgenerally ing the clearing time of prior circuit breakersfrom 11 cycles to 8 cycles indicate that there is but littlevpossibility of decreasing the operating time to less than about cycleswith the prior protective methods and circuit arrangements. The problemof constructing switchgear for the removal of an arcing fault from ahigh voltage line in from /2 cycle to2 cycles can be solved however byplacing on the feeder circuit an additional element which functions toreduce the line voltage at the fault to zero or substantially zero infrom /2 to 2 cycles, depending upon the magnitude of the fault current,after the initiation of the fault. An interruption of current flow thefault within from to 2 cycles will be referred to hereinafter as aninstantaneous removal" of the fault current, and this term is to bedistinguished from the term instantaneous tripping, which signifiesnothing more than the adjustment of the tripping relay to energize thecircuit breaker Vopening coil in as short a time as is possible. The newelement for use with existing switchgear or with the faster switchgearcontemplated by this invention will be termed a "line shorting contactoror shorting contactor as its function is to short circuit the linesafiected by a fault, therebyestablishing a low resistance short circuitthat develops the full short circuit current capacity of the transformerfeedingthe distribution circuit. This heavy flow of current simplifiesthe circuit breaker design by insuring adequate power for the rapidoperation of the breaker even in the case of a fault at a remote pointon a longline.- The instantaneous suppression of the initial faultcurrent substantially eliminates burn off from transient faults but doesnot solve the problems of protecting the overhead lines and associatedstation equipment, and of maintaining service 'on'other portions of thefeeder circuit inthe case of a permanent fault on a branch line. Theline shorting contactor supplements, but does not replace, otherequipment such as circuit breakers, or other tim- 1 ing devices thatreclose the circuit a plurality of times and for periods of upward of 30cycles in attempts to burn off the fault or the faulty branch circuit inthe case of a permanent fault. V

Objects of the invention are to provide novel apparatus for theinstantaneous removal of arc ing faults from power distribution lines.Further objects are to provide apparatus for the instantaneous removalof the line voltage at a'faulty section by first short circuiting andthen .opening the line, and for the subsequent reclosure v of the linefor relatively long periods and at timed intervals, up to a lockout inthe case of a pertional switch mechanism for successively energiz ingthe line to send current through the fault if it remains on the line,and for opening the line permanently in the case of a permanent fault.

These and other objects and advantages of the peres.

must be about 4500 ing times of certain apparatus of this invention:

Fig. 2 is a fragmentary elevation of insulated conductors of differentsizes showing limited damage caused by arcing faults that are suppressedin less than /30 second;

Fig. 3 is a fragmentary circuitdiagram of an electrical distributionsystem including protective equipment embodying the present invention;

Fig. 4 is a central section through a line shorting contactor;

Fig. 4c is a schematicdiagram of the same;

Y Figs. 5, 6 and 7 are sectional views of the coilshunting switch andtime-controlled latching mechanism of the line shorting contactor;

Fig. 8 is a central section of a circuit breaker having the rapidoperating characteristic of curve B of Fig. 1;

Fig. 8a is a schematic diagram of the same; and

Fig, 9 is an enlarged fragmentary view of the breaker contacts.

The novel features of the invention may be best understood by firstconsidering curves No. 6" to No. 1/0 of Fig. 1, that show the time, incycles on a cycles basis, in which arcing fault currents of differentmagnitudes burn off weatherproofed copper wires of the sizes indicatedby the legends identifying the curves. The conductors were tested underconditions of horizontal spacing and tension that simulated serviceconditions on a' 5000 volt feeder circuit, and the arcs were initiatedby drawing a No. 40 copper wire across bated sections of the conductors.The time values were obtained from an oscillograph and represent theactual parting of the conductors, i. e., they do not include the time ofarcin'gbetween the conductors as they fell away after parting.

The smallest size, No. 6 W. P. copper wire, is used on many long branchfeeder circuits where the normal load may be up to about 20 amperes andthe substation transformers have a short circuit current output ofupward of 1500 am- Curve No.- 6 shows that this small conductor willburn off in 2 cycles or & second under about 1700 amperes, while curveNo. 4 shows that the arcing fault current amperes to bum'oif a No. 4insulated copper wire in 2 cycles, and curve No. 2 shows that wire ofthis size will be burned oil in 3 cycles by an arcing fault of 5500amperes, or in '7 cycles by an arcing fault of 1500 amperes.

Thesignificance o1 thisfamily of curves is that arcing faults ofthemagnitudes encountered on various feeder circuitsof different wire sizeswill 55 manent fault; Objects are to provide line .protecting switchingequipment of high current caburn oil the conductors in the 8 or 10 cyclein tervalbetween the faultinitiation and the opening of the fastestswitching gear of the present commercial installations. -Furthermore, areduction of the breaker opening .time'tc 5cycle's' will i not efl'ectan appreciable reductionin the burn invention will be apparent from'thefollowing specification when taken with the accompanying drawings inwhich:

Fig. 1 is a curve sheet showing the relation between the'magnitudeof afault current and, respectively, the time required to burn oil.insulated conductors of different sizes and the operat-' oil or damagefrom arcing faults, and the present experimental attempts to obtain5cy'cle operation of a circuit breaker therefore will not eliminate theburn on of .insulated fconductor's by arcing flashoversdue to purelytransient faults Some damage resultsfroman'y arcing faul but the factoror. safety normally provided in- 0 good circuit design permits somereduction in the cross-section of the conductor without introducing aserious hazard of mechanical weah ess. Tests on many arc-burnedcopperwires of several sizes indicate that, in general,'the damage is notlikelyto result in breakage of wire by high wind or sleet loadings whenthe burn reduces the original cross-section by not more than about 25%.The limited damage resulting from arcing the main feeder circuit.

' aas'ra' cordance with this invention, is indicated by Fig. 2 in whichinsulated copper wires of sizes No. 2, No. 4 and No. '6 are identifiedby reference numerals 2, 4 and I5, respectively. The line voltage was5000 volts and the arcing fault current was 1500 amperes in the seriesof tests in which the specimens of Fig. 2 were obtained. The areingfault on the smallest wire 6 was removed in V2 cycle, and the arcingfaults on wires 2 and 4 were removed in 2 cycles. The illustrated arcburns b of the several conductors are typical of the results obtainedduring a systemmatic study of arcing damage to line conductors, andmechanical tests of similar specimens showed that burns of this order donot reduce the tensile strength of the wires below safe working values.

Reverting to Fig. l,'the curves A, A show the relation between faultcurrent and the operating time of line shorting contactors, to bedescribed later, of normal current ratings of 100 and 200 amperes,respectively, and curve B shows the opening time of a novel circuitbreaker contemplated by this invention. Overload currents of the orderof 1500 and 2500 amperes will actuate the line shorting contactor toclosed position, thereby collapsing the line voltage at the fault tozero, within substantially /2 cycle after the fault initiation. Curve Bshows that the new circuit breaker will open in 2 cycles at anyfaultcurrent above about I amperes. These operating speeds are substantiallyhigher than any previously attained on feeder circuits with switch gearthat is electrically and mechanically stable, and these high operatingspeeds for the instantaneous suppression of the fault current, bycollapsing the line voltage and/or opening the line, eliminate the burnoff of line conductors by transient faults.

A typical embodiment of the invention is shown in the Fig. 3 circuitdiagram of a substation and 5000 volt, 60 cycles feeder circuit workingout of a high voltage line X, Y, Z. The transformer T and regulator Rare or may be of conventional design. Reclosing circuit breakers CB areplaced on the several main feeder conductors at, 11, 2,, at thesubstation and may be of conventional design but preferably, as shown,are of a new instantaneously operating design and consist in fullyautomatic single pole circuit breakers that are self-contained andself-actuated. A line shorting contactor SC is also placed on eachconductor of the main feeder circuit, preferably at some distance fromthe substation to cushion the shock ,to be placed upon the stationequipment by the metallic short circuit that is placed upon the linewhen the shorting contactors are 'tripped' substation where the load hasbeen reduced by various branch circuits B that are connected to Thebranch circuits may be of No. 6 copper wire, either bare or insulateddepending upon local ordinances, and each branch is preferably protectedby fuses F.

'In the case of an important feeder branch 3',

the branch is preferably protected by repeater fuses RF.

The physical structure of a line shorting contactor SC is shown in Fig.4, and the elements and circuit connections are shown schematically inFig. 411. Each shorting contactor is a fully automatic, self-containedunit housed within a chamber comprising a hollow insulator II with upperand lower metal sleeves ll, I2, and top and bottom closures l3, [4 thatare bolted to the sleeves II, l2, respectively. The central portion ofthe insulator III is grooved or otherwise shaped to receive a supportingbracket l5 by which the shorting contactor is mounted on a pole orframework within a substation. A source or line terminal I3 enters theupper shell I l through an insulating bushing l1, and a load terminal I8extends through and is welded or otherwise me chanically andelectrically connected to the shell II. The operating coil IQ of thecontactor is connected between theterminals I6, l8 by straps 20, 2|,respectively, the coil l3 comprising a single or multiple layer solenoidwound from a flat copper bar. The coil I9 is mounted within a laminatedcore 23 that is secured between a pair of supporting plates 24 by bolts25, and the plates 24 are secured to and grounded on the upper metallicshell II by brackets 26. Thecentral section 21 of the laminated corerests upon a rubber cushioning member 23 to serve as a stop for theplunger, the cushioning member being carried by a plate 29 that isrigidly secured to the supporting plates 24. The armature or plunger 30comprises laminations riveted to ribs 30' that are welded to the switchrod 3i and project above the laminations to carry a part of the controlmechanism. The conical contact 32 on the switch rod 3| is axially alinedwith a conically recessed contact assembly comprising a plurality ofwedge-shaped segments 33 on leaf springs 34. The lower ends of thesprings 34 are secured to a cylinder 35 on a plate 36 that is supportedfrom the plate 29 by a plurality of insulating rods 31. A pressurecontact member 38 is connected to plate 36 by jumpers 39 and pressedinto engagement with the lower closure I4 by a spring 40. A terminal lug41 projects below the closure II for connection to similar lugs of theshorting contactors of other phases or to the conductor of a two-wirebranch other than that to which source and load terminals l6, l8 areconnected.

The hollow insulator is filled with oil to a level above the core 23,and a low resistance connection from the load terminal l8 to the movingcontact 32 is obtained through jumpers 32' that extend from contact 32to the \plate 23.

The upper end of the rod 3| extends through a strap 42 that is fixed tothe supporting plates 24, and a. spring 43 is coiled about the rod 3| tohold the rod in elevated position against the closing force developedlbycoil l9 at current flow less than a predetermined amount, for example50%, above rated current that the contactor can carry for long periods.

The source or line terminal I6 is connected to the stationary contact 44of a coil-shorting switch by the strap 20 and a jumper 45. The movableswitch contact 44' is carried by an arm 46 pivoted upon the supportingplates 24 and normally retained in open-circuit position by a spring 41that is anchored to plate 24 byasbolt adjustable along slot 41'. The arm46 is grounded on the load terminal l8 through the supporting plates andpreferably is connected to the plate 24 or to lead 2| by a jumper", seeFig; 4a. A closure of switch contacts 44, 44 will short circuit theoperating coil l9 and thus prevent operation of the shorting contactor.Time-delay mechanism, indicated. generally by the block 49, is providedfor retaining the switch 44, 44 in 7 closed position for a predeterminedinterval following a closure of the switch. I

The control mechanism for the shorting contactor is located between theupper ends of the supporting plates 24 and comprises a mechanicallinkage having parts mounted on the plates 24 and other parts pivoted tothe central ribs 30' of the laminated core. The control mechanism isillustrated in Figs. -7 as viewed from a plane through the axis of therod 3|, except that the timing mechanism is shown in elevation at theright of Fig. 5 and in Figs. 6 and '7.

The movable contact arm 46 comprises a pair of duplicate members mountedon plates 24 by a pivot pin 5| and joined at their outer ends by a strap46 which carries the contact 44'. A link 52, also pivoted on pin 5|, iscoupled to the contact arm 46 through a hairpin spring 53 that urges thecontact arm 48 clockwise when link 52 is rotated clockwise by a plunger.A pivot pin '54 connects the other end of link 52 to a latch member 55and extends through an elongated slot in a link 56 that is pivoted tothe core plate 30'. The upper end of the latch member is cut back forlocking engagement with a roller 51 on the pivot pin of a lever 58, thelatch member being pressed toward the roller 51 and a latchreleasing pin59 on lever 58 by a spring 69. The forked outer end of lever 58 receivesapin 5| on a timing lever 62 carrying a pawl 63 that bears on ratchetwheel 54 on the shaft of an escapement mechanism of conventional type,indicated by the block 49. Pawl 63 drives the ratchet wheel clockwisewhen lever 62 is rocked in that direction by a spring 65, and rides idlyover the-ratchet wheel when the lever is moved counterclockwise by alink 65 having an elongated slot receiving a pin 61 on the core plate30. The core plate 30 has an inclined slot, defined by'a notch in theplate and a projection 68, for receiving a roller 69 on a hold-off" linkthat is pivoted to the supporting plates 24 and urged clockwise towardsa stop pin III by a spring 12.

The control mechanism operates in the following manner. The arm 46 isnormally held in raised position by the spring 41, and the roller 59 oflink 10 is seated in the inclined slot of the core plate 3ll', as shownin Fig. 5. A predetermined current flow through coil l9 overcomes thespring 43 and moves the core 30 and rod 3i downwardly to close theshorting contactor, and the several parts'then have the positions shownin Fig. 6. Link 56 moves the latch member 55 down into lockingengagement with the roller 51, and rocks the link 52 clockwise to stressthe spring 53 that urges the contact arm 46 towards closed position. Thedrop of the plunger released the roller 69 of link Ill from the slot inthe core plate 30, and thereby forced link III, in conjunction with thespring 12, clockwise to the stop I I. This brought the upper end of link10 into the path of the bar 46' of the contact arm 46 and thus preventeda closure of the coil-shunting, contacts 44, 44'. Link 66 moved thetiming lever 62 counterclockwise and thereby stressed the spring 65 thatis to restore the timing lever to normal position with a time-delay thatis controlled by the escapement mechanism 49. The latch-release pin 59is now spaced from the latch member 55.

Upon the first opening of the circuit breakers CB, the rod 3| is liftedby the spring 43 and the parts assume the positions shown in Fig. 7.Link 52 cannot move up as it is locked by the engagement of latch member55 with the roller 51, and

the stress in the spring 53 tends to move the contact arm 46 clockwiseto close contacts 44, 44'. This closing motion takes place as soon asthe core assembly moves upwardly to force the roller 69 of link Ill intothe inclined slot by the projection 68. The elongated slot in links 86permits the core assembly to lift, but the counterclockwise movement ofthe timing lever 58 is retarded by the escapement mechanism 49 since thetiming lever is locked to the escapement mechanism by the pawl 53 andratchet wheel 54. The time-delayed return movement of the lever 58displaces the pin 59 into engagement with the latch member 55 to forceit out of locking engagement with the roller 51. When released fromroller 51, the latch member 55 is moved upwardly by the spring 53 thusreleasing the stress in that spring and thereby permitting the spring 41to rock the arm 46 counterclockwise to open contacts 44, 44'. Theequipment is thus reset to the condition shown in Fig. 5 after atime-delay determined by the escapernent mechanism 49. The time-delay issuflicient, as stated above, to permit the reclosing circuit breaker CBto operate through a predetermined time-delay to a lookout in the caseof a permanent fault on the line.

It is to be noted that, upon the initial removal of current by thecircuit breaker, the shorting contactor is locked out electrically bythe switch 44, 44' that shunts the coil I9, and mechanically by roller'69 and its supporting link Hi that is blocked against clockwisemovement by the strap of the closed contact arm 46.

The tripping current of the shorting contactor is determined by thenumber of turns of the coil l9, and the forces exerted by springs 43,41, 53 and 65. The lockout period is determined, for

\ any given escapement mechanism, by the force developed by the spring65 and by the gear train in the escapement mechanism. A control of theoperating characteristics is readily attained by adjusting thecompression of spring 43 by the downward or upward movement of thelocknuts on the end of the rod 3!. The spring 43 opens the shortingcontactor in about 5 cycles after the circuit breakers open, but theexact opening time is not important since the first reclosure of thecircuit breaker is delayed for from 30 to 60 cycles as a protectionagainst multiple lightning strokes. The shortingcontactor must openunder no-load, however, as the simple design which facilitates aninstantaneous closure makes 1 no provision for extinguishing an arebetween the main contacts. a

The operating speeds indicated by curves A, A of Fig. 1 have beenobtained in mechanically stable equipment such as shown in Fig. 4, andtrial installations have fully demonstrated that insulated conductorscan be protected from burn off from transient faults when the linevoltage is removed from the fault in /2 cycle. The line shortingcontactors do not, and are not intended to, protect the conductorsagainst burn off in the case of a permanent or relatively permanentfault. The maximum service is maintained and the location of a permanentfault is most readily ascertained, when the faulty branch circuit isisolated by sectionalizing fuses or is burned oil during the sequence ofoperations of a reclosing circuit breaker prior to a final lockout.

The shorting contactors may be used with any station breakers of thereclosing type but the maximum protection is obtained when the circuitbreakers CB are of the type shown diagramfaults between the substationand the shorting contactors which, as stated above, are preferablylocated some distance from the station to reduce the shock to stationequipment by the dead short circuit produced by the shorting contactors.Furthermore, the new circuit breakers afiord substantial protectionagainst burn ofi during the lookout time of the shorting contactorsafter a closure arising from a transient fault. The shorting contactorsmay be out of action for about, 3 minutes in such cases since service isrestored at the first reclosure of the circuit breaker. Lightningstrokes during this interval will usually result in a burn ofi when thecircuit breakers are of prior types and open in from 10 to 40 cycles,

but this damage is prevented when the new circuit breakers are used withthe line shorting contactors.

full automatic operation. As shown in Fig. 3a,

the circuit breaker includes a tripping coil 89'and operating coil 8| inseries between terminals 82, 83, the operating coil 8| being normallyshunted by the switch 84 that is opened by the tripping coil 99 againsta spring 84'. This switch and the main breaker switch are of thereciprocating rod type, as described and claimed in my prior Patent No.2,167,665, granted August 1, 1939, "Circuit breaker," in which anannular arc-extinguishing chamber is formed by horn fiber or otherorganic material which gives off de-ionizing gases when vaporized by thearc.

The core or plunger 85 of coil 8| is secured to a metal rod 86 whichcarries the movable contact 81 of the circuit breaker and terminates ina rod 88 of horn fiber or the like. The stationary breaker contactsinclude a main contact 89 that is normally engaged by the rod 86 or itsmovable contact 81, and an arcing contact 99 above and spaced from themain contacts. The arcing contact 99 is connected to the main contact 89through a spiral coil 9| coaxial with the rod 86 and the contacts. Thefunction of coil 9| is to rotate the arc that is drawn between themoving contact 81 and the arcing contact 99 when the breaker opens, andthe coil is wound in the sense oppositethat of the operating coil 8|.The shunt or tripping switch 84 is of simpler design as the are drawnacross its contacts can be extinguished without the aid of anarc-spinning coil.

Timing mechanism 92 is provided to delay the second and subsequentopenings of the breaker,

but the firstlopening takes place with no delay.

The timing mechanism is indicated generally by the block diagramoverlyin the junction of the operating lever 93 ofswitch 84 and the link94 that connects lever 93 to the armature 95 of the trip coil 89. Anydesired type of mechanism may be employed to delay the opening of theshunt switch 84 for intervals of 69 cycles or upward when the fault isstill on the line at thefirst or subsequent closures of the breaker. Thedetailed construction is not illustrated since it forms no part of thepresent invention.

The breaker is housed within a chamber comprising a hollow insulator 98and end closures 91, 88 of metal that carry terminals 82, 83,respectively. The insulator is provided with metal fiber plates or disksI94,

sleeves 99 to which the closures are bolted. and is recessed to receivea mounting bracket I99. A plate I9I extends across the-upper end of theinsulator 96 and constitutes the support for the trip mechanism and thebreaker assembly, and the control mechanism is located in the domedclosure 91 above the plate I9I. The insulator 9B is preferably filledwith oil to approximately the lower face of the plate I9I that supportsall 01' the switch and control mechanism.

The framework of the breaker assembly includes a series of rods I92, 2.metal plate I93 on which the coil BI rests, and a plurality of hornInsulating rods I95 are threaded upon rods I92 to secure the plate I93against spacing sleeves I95 on rods I92, and rods I92 are threaded uponthe rods I95 to carry the disks I94. A dashpot for arresting the openingmovement of the breaker is formed by the enlarged lower end of the'core85 and a-cylinder I98 that is'mounted between the plate I93 and theupper disk I94. The top portion of the cylinder flares inwardly abovevent openings that permit a free escape of oil from within the cylinderduring the major part of the opening movement of the rod 86.

The two intermediate plates I94 are separated slightly and are recessedto receive small horn fiber disks I94 that form the outer wall of thearc-suppressing chamber. The small plates may bereplaced when thediameter of the chamber has been appreciably increased by thevaporization of the horn fiber. The arc-spinning coil 9! is mountedbetween the two lower disks I94, and connected between arcing contact 99that is recessed into the lower face of the upper disk of this pair' anda flanged brass tube I98 that is bolted to the bottom disk I94 tosupport the main contact assembly. The main contact 89 includes aplurality of arcuate segments secured to the upper ends of the severalsections of a longitudinally slotted tube I99 of resilient metal. Theflanged lower end II9 of the tube I99 is electrically connected to adisk I I I by a jumper I I2, and the disk I I I is pressed against aboss on the lower closure 98 by springs I I3 coiled about guide rodsthat extend through the flange I I 9.

The breaker opens against a spring H4, and displaces a rachet bar II5into engagement with the wheel II6 of an escapement mechanism. Thespring II4 tends to reclose the breaker as soon as the circuit opens butthe downward motion of the switch rod 86 is delayed by the escapementmechanism. The escapement may be of known types, including means forlocking the breaker in open position after a. predetermined number ofreclosures if the fault is still on the line and means for resettingfrom any point in the schedule of reclosures when the breaker closes ona sound line. The time-delay may be of the customary order of from 30 to60 cycles, but the specific design of the escapement mechanism is not anessential feature of this invention.

It is to be noted that theline current flows through the seriesoperating coil 8| only when the shunting switch 84 is opened by the coil89. The tripping current is determined by the coil 89 and the reclosingspring 84' of the shunting switch 84. The tripping value may be adjustedas desired but will usually be set up to 200% or more of the ratedcurrent capacity of the breaker. Heat developed in the coil 89 bycontinued overloads short of the tripping value does not cause seriousheating and coil destruction, as has been the case with some priorbreakers with series operating coils, since the coil 80 opens only theshunting switch 84 and not the breaker contacts.

It is therefore possible to design the operating coil II to developsufllcient force for an exceedingly high speed opening of the breakersince only a momentary current surge flows in the operating coil. Thereciprocating rod and de-ionizing chambervconstruction also contributeto high speed operations as a 1 to 2 inch movement of the rod, which issufficient to separate the contacts and suppress the arc, is obtained inabout 2 to 3 cycles with operating coils ll of practical design. Theinitial opening of the breaker is effected in from 2 to 3 cycles inaccordance with the magnitude of the fault current, as shown graphicallyby curve B, Fig. l,

but the subsequent openings are delayed by the timing mechanism 92 tosupply current to a persistent fault for periods of 30 cycles andupward, thereby to blow sectionalizing fuses if the fault cannot beburned off. This results in the isolation of the faulty branch butservice is maintained on the remainder of the feeder system.

The method of operation of the protective equipment is as follows. Thecircuit breakers are adjusted to trip at a selected overload value,which may be, as in present practice, about 200% of the rated currentcapacity of the breaker, and the line shorting contactors are set totrip at a lesser overload. Any fault that results in the predeterminedoverload at the line shorting contactors thus trips the contactors toplace a metallic short circuit across the affected conductors in $6cycle after the fault initiation.

This instantaneous suppression of the fault current prevents the blowingof fuses and the burn oil of insulated conductors at the fault. In thecase of bare wires, the instantaneous suppression of the fault currenteliminates damage to the supportingstructure when a traveling arc startsclose to and would reach the supporting structure before it is blownout. The circuit breakers are tripped either by the initial faultcurrent or by the heavy current flow through the closed contactors SC,and reclose after a delay or from 30 to 60 cycles which permitsde-ionization of the gases in the region of the arc path. The shortingcontactors open with the interruption of current flow by the circuitbreakers, and are locked out for a predetermined time during which thecircuit breakers go through a series of timedelay trip operations tolockout in the case of permanent faults.

- The sequence of operations varies with the nature of the fault I on afeeder circuit B. If the fault was due to a transient cause, such aslightning or a small wire dropped across the line, the circuit breakersstay in on the first reclosure. If the fault is'still on the line, theheavy current flow tends to burn oil" the fault I and to blow the fusesF. The feeder circuit itself may burn off before or simultaneously withthe burning of the foreign object that is across the line. If the lineis not cleared by one of these methods, the fuses blow to remove thefaulty section from the feeder system before the circuit breakerscomplete a full sequence of reclosures to a lookout, and service isthereby restored to the remainder of the feeder circuit. Theinstantaneous closure of the shorting contactors protect the fusesagainst damage before the first opening of the circuit breakers, andthereby affords greater latitude in the selection of the time-responsecharacteristics of sectionalizing fuses. The fuses will usually blowdurl2 ing the first reclosure of the circuit breakers in the case of apermanent'fault.

Protection against bum oil is obtained whether the circuit breakers areof the described construction or of prior designs that require at least8 cycles to open. The Fig. 8 circuit breakers afford greater protectionagainst an outage of a part or all of the feeder since they open inabout 2 cycles.

' The existing substation equipment may be such that the line shortingcontactors should be located a mile or more from the station to reducethe shock placed on the station equipment by the metallic short circuit.The impedance gradient of the line to the short circuit point reducesthe current drawn by ashort circuited line, and the maximum shortcircuit current at a given substation can therefore be controlled tosome extent by locating the shorting contactors some distance from thestation. The preferred spacing will de-.

pend upon such factors as the capacity of th station equipment and ofthe line feeding it, the standards of operation established by thepublic utility company, and the type of service fed by the protectedcircuits. The shorting contactors can be located at the substation insome cases but at other stations the preferred location may be from onemile up to two or three miles from the station. This means that aportion of the feeder is not protected by the shorting contactors, butthe reclosure is on a clear line.- Another lightning stroke during thelookout period of the shorting contactors will usually result in a burnoff when the breakers are of the prior designs but the high openingspeed of the new breakers will usually protect even the smallerinsulated a burn on. v

The new-circuit breakers maybe used without 1 the shorting contactorsbut the full advantages of the invention are attained when a feedercircuit is protected jointly by the new circuit breakers and the lineshorting contactors.

It is to be understood that adequate protection against burn off fromtransient faults may be had on some feeders when the fault currentcontinues for more than from to ,2 cycles, but equipment with this highoperating speed is readily manufactured and there is no advantage to begained by designing the equipment for a longer operating time. D

Time values are stated in cycles on a 60 cycles per second basis sinceit is the usual practice in this art to measure the operating times ofprotective switchgear with oscillographs that generate a "timing wave"of the frequency of the electrical distribution system. The novelequipment of this invention was tested and has been used on linessupplied with alternating current of a frequency of 60 cycles per secondbut the protective methods and apparatus may be used on direct currentlines or alternating current lines energized at 25 cycles per second orat other frequencies. I

Claims specific to the line shorting contactor and to the reclosingcircuit breaker herein illustrated and described have been presented indivisional applications Serial No. 438,823, filed April wires against13, 1942, on which Patent No. 2,334,571 issued November 16, 1943, andSerial No. 439,576, filed April 18, 1942, respectively.

The circuit arrangement or combination of protective devices hereinshown and .described is illustrative of the invention, and variouschanges that may occur to those familiar with the art fall within thespirit of my invention as set forth in the following claims.

I claim:

1. In an electrical distribution system, the combination with a currentsource, conductors extending from said current source to form adistribution circuit, reclosing circuit-interrupting means responsive toa fault on said circuit to effect the first opening thereof after a timedelay during which arcing conduction resulting from a fault will damagethe conductors, said circuit-interrupting means including controlmechanism for opening and reclosing the circuit a plurality of times toa final lockout in the event of a permanent fault, of means to protectsaid conductors against damage from transient faults; said protectingmeans comprising a normally open switch across said conductors, springmeans biasing said switch to open position, means responsive to a faultcurrent to close said switch prior to the first opening of saiddistribution circuit by said circuit-interrupting means, thereby toestablish a metallic short-circuit across said conductors and remove thevoltage from the fault point, said spring means opening said switch toremove said metallic short-circuit upon opening of said distributioncircuit by said circuit-interrupting means, said control mechanismincluding means to delay the first reclosure of saidcircuit-interrupting means until said switch is opened to remove saidmetallic short-circult, and timing means to lock said switch againstreclosure during the time period required for operation of saidreclosing circuit-interrupting means \to a final open position in theevent of a permanentfault.

2. In an electrical distribution system, the combination with reclosingprotective apparatus for opening the system after a time delay of froml/30 second to about 1 second after fault initiation and to reclose thesystem a plurality of times to a lockout in the event of a permanentfault; of

time-delay means energized upon the opening of slid switch by saidspring means to prevent a reclosure of said switch within the timeinterval required for operation of said reclosing protective apparatusto a lockout in the event of a permanent fault,

3. In an electrical distribution system, a current source, conductorsextending from said source, and branch circuits connected across saidconductors through circuit interrupters including thermally responsivemeans for opening the same after a time delay interval in the event offaults on the respective feeder circuits, of protective means topreclude opening of said interrupters from transient faults; saidprotective means comprising a normally open shorting circuit connectedacross said conductors between said branch circuits and said currentsource, a line shorting contactor for closing said shorting cir-- cuit,and means responsive to fault current flow to actuate said shortingcontactor to closed position within a time interval substantiallyshorter than the time delay interval within which said circuitinterrupters may open, thereby. to collapse the voltage at the faultpoint to zero, and means for opening said shorting circuit after apredetermined time interval.

4. In an overhead power distribution system, a source of current, a pairof overhead conductors forming a circuit fed from said current source,means including a normally open switch operative to closed position by afault current to shortcircuit said conductors, circuit interruptingmeans responsive to the fault current and the short-circuit current toopen said circuit, means responsive to the opening of said circuit bysaid circuit-interrupting means to render said short- ,circuiting meansinoperative for a predetermined period after the initial operationthereof, and control means operative within said predetermined period toreclose said circuit-interrupting means a plurality of times prior to afinal opening thereof in the case of a permanent fault.

5. In an electrical distribution system, the conibination with a currentsource, conductors forming adistribution circuit fedfrom said source,and circuit-interrupting means responsive to overload current flow andincluding mechanism for opening and reclosing said circuit a pluralityof times priorto a final opening thereof in the event of a permanentfault, of a shorting circuit across said conductors including a normallyopen shorting switch having contacts permanently connected to therespective conductors, means responsive to fault current flow to closesaid shorting switch prior to the initial opening of the distributioncircuit by said circuit-interrupting means, means to open said shortingswitch in the interval between the initial opening and the firstreclosure of the distribution circuit by said circuit-interruptingmeans, and timing means to lock said shorting switch in open positionfor a period longer than the operating time or said circuit-interruptingmeans to a final cirsaid circuit and to reclose the same a plurality oftimes for intervals of the order of at least second, 'of means toprotectsaid conductors from damage in the case of transient faults; saidprotecting means comprising means to shortcircuit; said conductors priorto the initial opening of the circuit -by said circuit-interruptingmeans, means operative upon the initial opening of the distributioncircuitto remove the shortcircuit, and means to lock saidshort-circuiting means against operation for a predetermined periodafter the removal of the short-circuit, said predetermined periodextending over a plurality of opening and reclosing operations of saidcir. cuit-interrupting means.

7. In an electrical distribution system, the combination with analternating current source, a feeder circuit connected to said currentsource, and circuit-interrupting means of the reclosing v 15 type onsaid feeder circuit, said means including mechanism responsive toexcessive current flow to open and to reclose said circuit-interruptingI means a plurality of times, a line'shorting con-'- v 'tactor for shortcircuiting the feeder circuit; said line shorting contactor includingmeans respon-p sive to excessive current flow to operate said cona closesaid second switch.

tactor to short circuit the feeder circuit prior to the initial openingof said circuit-interrupting means and within second after a faultinception, means to operate said contactor to remove the short-circuitupon the initial openins of said circuit-interrupting means, and timingmeans to lock said contactor in open circuit condition for apredetermined period following an operation thereof to open circuitcondition.

8. In an electrical distribution 'system, the in-, vention as claimed inclaim "I, wherein said clifcuit-interrupting means comprises a reclosingcircuit breaker between said current source and said feeder circuit. 1

9. In an electrical distribution system, the in- 'vention as claimed inclaim '1, wherein said cir-,

cuit-interrupting means comprises repeater fuses on said feeder circuit.

. 10. In an electrical distribution system, the combination with analternating current source, an overhead feeder circuit includinginsulated conductors, a circuit breaker betweensaid current source andsaid feeder circuit, and means responsive to excess current flow to openand to reclose said circuit breaker a plurality of times, 1 of anormally open switch connected across said feeder circuit, meansresponsive to excess current arising from a fault to close said switchwithin one cycle after fault inception, means to open said switch uponthe'initial opening of the feeder contactor upon the initial opening ofsaid cir- I circuit by said circuit breaker, and means for retainingsaid switch inopen position for a period corresponding to a plurality ofreclosures of said circuit breaker after the initial operation thereof.

11. The invention as claimed in claim 10, wherein said means for closingsaid switch in- Number '12. In an electrical distribution system, thecombination with an alternating current source, a feeder circuit, acircuit breaker including means to open the same in response to a faulton the feeder circuit, and time-delay means for reclosing the circuitbreaker, of a normally open line shorting contactor connected across thefeeder circuit, means including a coil in series with said feedercircuit to close said contactor instantaneously upon fault inception,means to open said cuit breaker, locking means to retain said contactoropen after a cycle of closing and opening thereof due to a fault on thefeeder circuit, and time-delay means for rendering said locking meansinoperative.

13. The invention as claimed in claim 12, wherein said locking meansincludes a switch .for shunting said coil.

14. The invention as claimed in claim 12, wherein aid locking meansincludes a mechanical latch for locking said contactorin open position.

15. The invention as claimed in claim 12, wherein said locking meansincludes a switch for shunting said coil and a mechanical latch forlo'cking said contactor in open position.

v .GEO. A. MATTHEWS.

naraaancas crran The following references are of record in the fileofthis patent:

UNITED STATES PATENTS Name Date Nicholson Oct. 1'7, 1916

